34 THE SURGICAL ANATOMY OF THE HORSE 



This is most frequently the cause, although in some cases the alveolus 

 may fill up and the tooth be pushed out from its socket more quickly 

 than the remaining teeth. In the natural course the filling up of 

 the several alveoli proceeds at a uniform rate. 



It is usual in such cases to give the row of teeth an even bearing by 

 clipping off the overgrown part. For this purpose an instrument called 

 a "tooth-shears" is used. It will be evident that the further in the 

 mouth the affected tooth is placed, the more difficult does the opera- 

 tion become. In fact, when further back than the third molar, the 

 operation is one which presents considerable difficulty. 



Shear Mouth 



This is the term which is applied to the condition wherein there is 

 such irregularity in the wear of the teeth, that the tabular surfaces 

 present a very much exaggerated degree of inclination. The outer 

 edge of the upper molars continues to grow to such an extent that it 

 frequently injures the gums of the lower jaw. Similarly the inner edge 

 of the lower row may reach and lacerate the palate. 



In addition to the liability to injury of the parts named, there is 

 marked want of ability to effectively masticate the food. 



The condition depends to a great extent upon the conformation of 

 the lower jaw, those cases in which the two rami approximate too 

 closely to one another being specially predisposed to the affection. 



Occasionally only one or two teeth are affected, but usually the 

 condition affects all the molars. In the latter cases very little can be 

 done, especially if the cases are advanced. In those cases where the 

 condition is limited to one or two teeth, excision of the faulty tooth or 

 teeth by means of a tooth-shears is practised. The tooth-shears is a very 

 heavy instrument, and care must be taken whilst using it not to split 

 the remaining portion of the tooth, or to fracture the edge of the 

 alveolus. 



